The use of foam for marking crops is generally used for marking the edges of spray swaths when applying fertilizer or pesticide solutions to crops. The application of a foam line enables an operator to demark areas of a crop which have been treated with a spray application to ensure proper alignment of the spray swaths upon reentry into the field. Foam is generated on the back of a tractor or a towed implement and utilized to mark the edge of the spray application to ensure the crops are not treated twice.
In general there are two types of conventional foam generating systems that are utilized for foam marking operations. The first system is commonly referred to as a "tank mix" system. In this system, foam marker solution and air under pressure are combined. The air supplied to the solution under pressure provides two actions. First, air injected into the foam concentrate, causes the concentrate to form a thick foam. Second, the air pressure forces the produced foam through the distribution lines.
The second type of system utilizes "generating tubes." In this system, air under minimal pressure is used to move foam marker solution from the mix tank to the generating tubes. At the same time that the mixed foam solution enters the tops of these tubes, air under optimum operating pressure is injected into the bottoms of the tubes thus mixing with the foam solution and creating the foam. Again, the injected air acts to push the foam through the distribution lines.
In both types of systems, there are some similarities. The amount of mixed foam solution compared to the amount of air being injected can be varied. Doing such can create foam quality varying from wet and heavy to dry and light, each having its advantages and disadvantages. The frequency in which the air is injected into the system can be varied as well. In foam generating equipment, the air injection oscillates between "on" and "off" according to settings chosen by the equipment operator. This allows for variation in spacing between foam droppings.
In agricultural marking applications, the foam is translated through the distribution line or hose extending from the foam generation equipment to the end of a boom where the foam is applied to the crop. The foam may be applied to the crop directly from the hose, or through an intermediary collection or dispersion cup attached to the end of the hose.
A typical dispersion cup is bell shaped or frusto conical having an opening attached to the distribution line and a second larger opening. The foam collects within the cud forming the foam droppings to be applied. In a typical system the compressor is run intermittently to allow foam to accumulate within the dispersion cup, after which it falls from the cup marking the crops with a single blob. In this manner, blobs of foam are dropped periodically to mark the outer area of the crop which has been treated. Both foam generating systems described above contain two sets of lines depositing foam, one each on the left and right sides of the equipment. The hose through which the foam is discharged may be selectively changed depending which way the tractor is traveling.
Under normal circumstances, current foam producing equipment works for pre-emergence applications on all types of crops, but only for post emergence applications on some. The prior art as described works satisfactorily on pre-emergence crops by discharging a drop or blob of foam upon the ground. However, in post-emergence crops the drop or blob of foam is too heavy to rest on top of the foliage. As a result, the foam falls to the ground between the rows of crops, instead of resting on top of the leaves where it would be visible to the operator. If the blob of foam is light enough to rest on top of the leaves, it dissipates or blows away before the operator reaches the end of the field, turns around, and guides back along the marks.
Consequently it would be desirable to have a foam marking apparatus and method that would allow for application of foam on both pre-emergence and post-emergence crops. It would also be desirable to have a foam marking system that would allow for foam to be applied in a continuous line as opposed to a series of drops.